1. Technical Field
The present application relates generally to an improved data processing system and method. More specifically, the present application is directed to a system and method for creating and managing multiple virtualized remote mirroring session consistency groups.
2. Description of Related Art
With today's businesses being increasingly more dependent on computing and storage systems for the maintenance and use of business related information, disaster recovery is of considerable importance. Thus, many different disaster recovery mechanisms have been devised to help ensure the access ability of businesses and individuals to their data even in the event of a failure of their storage systems.
One such disaster recovery mechanism that has been developed is the Global Mirror™ disaster recovery solution available from International Business Machines, Inc. of Armonk, N.Y., which is available on IBM's enterprise storage devices including the DS8100, the DS8300, the DS6800, the ESS Model 800 and the ESS Model 750.
Global Mirror™ provides a long-distance remote copy solution across two sites using asynchronous technology. The Global Mirror™ solution provides the ability to mirror data between volume pairs of a storage unit over greater distances without affecting overall performance. Global Mirror™ is also designed to provide application consistent data at a recovery (or remote) site in case of a disaster at the local site. By creating a set of remote volumes every few seconds, the Global Mirror™ solution addresses the consistency problem that can be created when large databases and volumes span multiple storage units. With Global Mirror™, the data at the remote site is maintained to be a point-in-time consistent copy of the data at the local site.
Global Mirror™ is based on the existing copy services functions Global Copy™ and FlashCopy®. Global Mirror™ operations periodically invoke a point-in-time FlashCopy® operation at the recovery site, at regular intervals, without disrupting the I/O to the source volume, thus giving a continuously updating, nearly up-to-date, data backup. Then, by grouping many volumes into a session, which is managed by a master storage unit, one can copy multiple volumes to the recovery site simultaneously while maintaining point-in-time consistency across those volumes.
In the Global Mirror™ solution, the master storage unit controls the creation of consistency groups in a Global Mirror™ session. The master storage unit sends commands to subordinate storage units. A storage unit is allowed to be a master for only one Global Mirror™ session.
The subordinate storage unit receives commands from a master storage unit. The subordinate storage unit is identified when a Global Mirror™ session is started. The subordinate storage unit forms consistency groups and performs other Global Mirror™ processing. A subordinate storage unit can only be controlled by one master storage unit.
A session is a collection of volumes across multiple storage units that are managed together to create consistent copies of data. The session is identified with an ID that is unique across the enterprise. The ID identifies volumes that will participate in the Global Mirror™ consistency group. For disaster recovery, it is required that the volumes in a session that are necessary for recovery be consistent up to the time of failure. If data on these volumes is copied out of sequence, then the recovery procedures that use these volumes become useless.
A control path is established from the master storage unit to a subordinate storage unit when more than one storage unit participates in the Global Mirror™ session. A separate control path may be provided between each master storage unit and each of its corresponding subordinate storage units. The master storage unit communicates directly with its subordinate storage unit using the defined control path.
The automatic cycle in an active Global Mirror™ session works as follows to maintain data at a remote site to be a point-in-time consistent copy of data at the local site. First, consistency groups of volumes are created at the local site. Increments of consistent data are sent to the remote site and FlashCopy® operations are performed at the remote site. Global Copy operations are then resumed between the local and remote site to copy out of sync tracks. These steps are repeated according to defined time intervals.
Currently, the Global Mirror™ solution only allows one physical session to be running at a time per physical storage control unit, i.e. the control processor for the storage subsystem. This significantly reduces the business flexibility for businesses that may have multiple applications, sometimes with different service level agreements, on one storage control unit. That is, since only one physical session is allowed to run per physical storage control unit, if a scheduled failover or failback operation is desired by the user for a specific set of volumes, the failover or failback operation must be performed with regard to all of the storage volumes controlled by that physical storage control unit and thus, all of the applications that utilize the physical storage control unit.
Therefore, even though the failover or failback operation may be desired for the storage volumes for only one application, all of the storage volumes and applications must undergo the failover or failback operation. Thus, it would be beneficial to have a mechanism that allows individual storage volumes or individual sets of storage volumes associated with a single application to be the subject of a failover or failback operation within a physical session of a remote mirroring storage system, such as a Global Mirror™ based storage system.